Removal of contaminants such as minerals and ions from fluids such as water and waste water is becoming extremely important in preserving water resources. Examples of fluids, which may require removal of minerals and ions include surface, ground and process water and waste water from industrial plants, refineries and waste treatment plants. Ionic and metallic pollution in water destroys the ecological balance and can be a threat to human, animal, fish and plant life.
Water deionization and demineralization processes are well known. Examples of such processes include reverse osmosis, chemical precipitation, ion exchange, and distillation. Examples of processes for weak ion exchange water deionization and demineralization are shown in U.S. Pat. Nos. 3,905,903, 3,928,192, 3,939,071, 3,941,693, and 4,028,234, which are incorporated by reference herein. For example, in U.S. Pat. No. 3,905,903, a process for water demineralization is shown involving use of separate beds of weakly acidic cation exchange resin, weakly basic anion exchange resin, and a third column of weakly acidic cation exchange resin. The first column of cation resin is buffered with a suitable base such as ammonia or an amine. When the saline feed is passed through the system, the cations of the feed are exchanged for the buffer, releasing buffered salts. The buffered salts when passed through the anion exchange column are split, releasing the buffer that is then deposited on the third cation resin column. The latter weakly acidic cation exchange resin is then used as the first bed during the next demineralization cycle.
The present invention comprises improved methods of water deionization and demineralization comprising improved resins, buffers, regeneration and regenerant recovery systems which enable overall improved efficiencies and cost savings over prior art methods. The improved methods of the invention enable the systems of the invention to be utilized in a wide variety of commercial applications. The improvements to water deionization and demineralization processes disclosed herein include an improved overall process comprising regeneration, regenerant recovery and recycle steps enabling recovery and reuse of spent resins and regenerants. Further, the improvements comprise new anion resins, new amine buffers and new regenerants.